The constant cannot be marked static
c#
Solution
`const` implies `static` (you don't need an instance to reference the `const` value).
I want to also add this important point: When you link against (reference) an assembly with a `public const`, that value is copied into your assembly. So if the `const` value in the referenced assembly changes, your assembly will still have the originally compiled-in value.
If this behavior is not acceptable, then you should consider making the field a `public static readonly` field.
Lib.dll, provided as binary:
public class Foo {
public const int HATS = 42;
public static readonly int GLOVES = 33;
}
App.exe, references Lib.dll:
Foo.HATS // This will always be 42 even if the value in Lib.dll changes,
// unless App.exe is recompiled.
Foo.GLOVES // This will always be the same as Foo.GLOVES in Lib.dll
From MSDN:
Don’t create a constant to represent information that you expect to change at any time. For example, don’t use a constant field to store the price of a service, a product version number, or the brand name of a company. These values can change over time, and because compilers propagate constants, other code compiled with your libraries will have to be recompiled to see the changes.
From DotNetPerls:
DLLs. When you use a `const` field or declaration, the C# compiler actually embeds the `const` variable's value directly in the IL code. Therefore, it essentially erases the `const` as a separate entity.
Caution: If programs that depend on a `const` are not recompiled after the `const` value changes, they may break [because they'll continue to use the previous value].
Problem
I am trying to declare a PI constant like this: ``` public static const double PI = Math.PI; ``` but why am I getting this error? ``` The constant 'Calendar.NewCalendar.PI' cannot be marked static ```